Rubber bladed fan



July 5, 1938.

RUBBER BLADE!) FAN Filed Aug. '7, 1936 I 2 Sheets-Sheetl Inks 724 01EJwdFb d7 Frefloo 9% 4 E. s, PRESTON 2,123,146

y 1933- E. s. PRESTON 2,123,146

RUBBER BLADED FAN Filed Aug. 7, 19 36 2 Sheets-Sheet 2 Euvd rd /1; 0?

Patented July 5, 1938 UNITED STATES PATENT OFFICE Application August 7,1936, Serial No. 94,775

5 Claims.

My invention relates to the rotating fan-blade members of electric fans,its general objects being those of providing an easily and inexpensivelymanufactured assembly of fan blades with the hub member supporting theseblades, which will permit the fan blades to be of a suitably flexiblerubber so as to eliminate the need of a wire guard housing the blades.

Furthermore, my invention aims to provide a fan-blade member in whichflexible rubber blades are mounted on a frontal and forwardly taperinghub portion, the peripheral face of which hub portion guides part of theair to the blades so as to increase the efliciency of the fan. For thispurpose, my invention aims to provide a fan-blade member in which such aforward hub portion can either be moulded integral with the blades, orhave the inner end portions of the blades socketed into it so as topermit the said hub portion to be of a harder material than that of theblades.

In addition, my inventionv aims to provide a simple and effectiveassembly of such a frontal hub portion with a metal hub part adapted tobe attached to the shaft which rotates the fanblade member.

In manufacturing and selling household electric fans on a large scale Ihave found that the extensiveness of their use has been greatly retardedboth by the noise due to the interference of portions ofthe usual wireguards with the free movement of the air propelled by the fans, and bythe accidents which can readily cc cur if a finger of a hand enters theinterior of the wire guard. Furthermore, the manufacturing 'andattaching of 'a wire guard involves a considerable cost, and theobjectionable noisiness of electric fans is often caused either by aloosening of some portionof the guard-attaching provisions or by arelative lbosening of constituent portions of the wire guard.

My present inventionaims to overcome all of the above recited handicapsand objections, and particularly aims to provide a fan member which willnot be apt to injure the hands of children when used without any guardaround it, and which can readily be employed in connection with theusually employed fan motor constructions.

Illustrative of the manner in which I accomplish the above recitedobjects,- j

Fig. i-isa front elevation ota hub and fanblade member embodying myinvention, in which the blades and the blade-carrying frontal'hubportion-are integral.

Fig. 2 is side elevation of the same member.

Fig. 3 is a side elevation of the entire hub member, including the metalstem through which that member is attachable to a shaft, with dottedlines indicating the junctures of blades with the conoidal hub portionof the said member.

Fig. 4 is a rear elevation of the hub and fanblade member, drawn on asmaller scale than Figs. 1 and 2.

Fig. 5 is an'enlar'ged section through the central portion of the huband fan-blade member, taken along the line 5--5 of Fig. 1, and includingpart of a shaft to which that member is attached.

Fig. 6 is a front elevation of the head of the said metal stem, drawn onthe same seale'as Fig. 5.

Fig. 7 is a partially sectioned elevation of the shank part of the saidmetal stem, showing this as it appears when initially formed.

Fig. 8 is an elevation of an initially fiat rubber blade suitable forhaving its inner portion socketed in a notch in a separately formedconoidal hub part, drawn on the same scale as Fig. 1.

Fig. 9 is an elevation of'a separately manufactured hub member providedwith notches in. which the inner ends of blades, such as the one shownin Fig. 8, can be socketed, drawn on the same scale as Fig. 5.

Fig. 10 is afragmentary section, taken along the line Ifl-ll of Fig. 9.I

"In constructing the hub and fan-blade assembly of Figs. 1 to 5, I firstprovide a generally cylindrical stem shank I having an axial bore 2extending forwardly into it for receiving the forward portion of a motorshaft 3, and having a lateral and threaded bore near its rear end forreceiving a screw 4 to fasten the said shank to the said shaft. The stemshank I has its forward end portion la reduced in diameter so as topresent a forwardly facing annular shoulder i b, and this forwardportion is bored to constitute a thin-walled tube, as shown in Fig. 7.

Next I provide a disk-dike stem-head H (Fig. 6)

annular shoulder lb, and the forwardly projecting end of the saidtubular shank portion is thereafter expanded to clinch itagainstthe-face of the stem-head H as shown in Fig.5, thereby making this headeffectively integral with the shaft-supportable stem l.

Then, by using a suitable mold into a portion of which the rear end ofthe said stem shank is set, I mold the desirably conoidal hub portion Caround the forward parts of the said metal stem, in doing which therubber fills the bores of the stem-head so as to lock the stem againstrotation with respect to the rubber body of the said hub portion. With asuitably constructed mold. the blades B of the fan can readily be moldedin this manner simultaneously with the said hub portion, therebyexpediting the manufacture and causing my hub member to present afrontal central portion which, because of the yielding nature of therubber, will not damage a hand contacting with it.

Each such blade preferably decreases gradually in thickness from itstrailing edge to its leading edge, as shown in Fig. 2, thereby reducingthe flexing action of air pressure on the blade part near the leadingedge, but may have its extreme inner end portion of a uniform thicknessas shown by the dotted lines S in Fig. 3. The radial length of eachblade also preferably decreases gradually from the midwidth portion ofthe blade to its trailing edge, as shown in Fig. 4 by comparison with adotted are 9 concentric with the fan-blade member.

Each of the blades has its inner end, namely I the juncture of the bladewith the conoidal hub portion, extending spirally of the periphery ofthe said hub portion (asshown by the dotted lines S in Fig. 3) andconcaved forwardly to a sufilclently greater extent than that whichwould be required (if the blade were inflexible) for giving the bladethe desired curvature, or screw-thread pitch, such as that shown indotted lines at B in Fig. 2. This difference in curvature can readily bedetermined experimentally according to the flexing eifect'of the backthrust of air on a blade of a given grade of rubber at the speed of themotor shaft which is to rotate the blade member, so that the backpressure of the air moved by the blade will flex the blade from itsshaping B (when the fan is not running) to the effective operative shapeB of the blade.

Consequently, when the fan is rotating, each "an imaginary ficle T(shown dotted in Fig. 4)

of considerably smaller diameter than the rear end of the said hubportion C, and hasthe outer end of each edge curvedly connected to theradially outer end of the blade. Moreover, the trailing edge T of eachblade desirably has a straight portion tangential to an imaginary circleI (Fig. 1) of less diameter than the aforesaid circle I, the last namedstraight edge portion being shorter than the straight portion of theleading edge but also of more than half the entire length of the saidtrailing edge.

Moreover, the .part of each blade adjacent to both the leading edge L ofthat blade and the hub portion C desirably extends behind a portion ofthe next blade (as shown in Fig. l) and is sufflciently spacedrearwardiy from the latter portion to permit a part of the mold toextend into this space and to facilitate 'movement of air between theconsecutlve blades.

I also have found it desirable to have the straight portions of theleading and the trailing edge of each blade converge at an angle A(Fig. 1) sufiiciently less than 360 degrees divided by the number ofblades, so that the juncture S of the blade with the hub member will beadequately long to have the desired effect on the curvature of the facesof the blade. That is to say, for a four-bladed fan the said angle Athen is considerably less than 90 degrees, as for example only 65degrees in Fig. 1, so'lthat each of blade uncture portions S in Fig. 3extends along more than a quarter of the circumference of the hubportion 0.

Thus constructed, and with the spread ID of the inner ends of each bladenot more than half the maximum width ll of the blade, as shown in Fig.1, I have found my novel hub and blade member highly eflicient in afour-blade type as here illustrated. However, it should be obviouswithout separate picturing that either a smaller or a larger number ofblades might be used with the same hub member and with the bladesotherwise disposed as previously described.

Likewise, instead of molding the blades integrally with the conoidal hubportion by a single operation, the blades of my novel hub and blademember may initially be formed separately and thereafter attached to thehub part. To accomplish this after the manner of Figs. 8 to 10, I formthe conoidal hub part C (while molding it around part of the metal stem)with surface grooves I! as shown in Fig. 9, each of which groovescorresponds in shape and spiral pitch and position to one'of the bladeand hub juncture outlines S in Fig. 3, and each of which grooves is ofsufficient depth to house an inner end portion B of a blade which iscorrespondingly lengthened at its inner end as shown in Fig. 8. Then Iinsert the inner end of each blade into one of the said slots and anchorit there by means of a rubber cement or the like. By proceeding in thejust recited alternative manner, I can have the bladesupporting hub partvulcanized to a greater extent than the blades, so as to give this hubpart a smoother exterior which will produce less friction; and with suchseparately formed blades the blade-supporting part could also be made ofmetal, plastic composition or other solid material.

So also, while'I preferably make the blade-supporting part of my hubmember of a forwardly tapering conoidal shape, this shape may be varied,as also the provisions for fastening the said part to the shaft of themotor, and many other changes obviously might be made without departingeither from the spirit of my invention or from the appended claims.

I claim as my-invention:

1. An impeller of the class in which blades are supported by and projectradially from a hub of molded material, a hub and stem assemblycomprising a metal stem having its rearward portion constructed forattachment to a shaft coaxial with the stem; the stem having its forwardpart extending axially into and imbedded in the molded material of thehub, and having a portion of the said imbedded part shaped so thatportions of the molded material in which the said portion is imbeddedwill prevent a relative movement of the hub with respect to the stemboth 2. An impeller of the class in which blades are supported by andproject radially from a hub of 7 molded material, a hub and stemassembly comprising a metal stem having its rearward portion constructedfor attachment to a shaft coaxial with the stem; the stem having adiametrically enlarged forward portion imbedded in the molded materialof the hub, the said enlarged stem portion having bores in whichportions of the molded material are also imbedded.

3. An impeller of the'class in which blades are supported by and projectradially from a hub of molded material, a hub and stem assemblycomprising a metal stem having its rearward portion constructed forattachment to a shaft coaxial with the stem; the stem having adiametrically. enlarged forward portion imbedded in the molded materialof the hub, the said enlarged stem portion having bores extendingthrough it parallel to the axis of the stem, and filled with portions ofthe molded material of the hub.

4. In an impeller of the class in which blades project radially from ahub of molded material, a stem member coaxial with the hub and havingits forward part imbedded in the material of the hub; the stem membercomprising a shank having a diametrically reduced forward facing annularshoulder adjacent to the rear end of the said diametrically reducedportion, and a centrally perforated head sleeved upon the said reducedportion and bearing rearwardly against the said shoulder, the saidreduced portion of the said shank having its forward end expanded toclamp the head rigidly against the said shoulder.

5. In an impeller of the class in which blades project radially from ahub of molded material, a stem member coaxial with the hub and havingits forward part imbedded in the material of the hub; the stemcomprising a shank having at its forward end a diametric enlargementpresenting a forward face and also presenting a rearwardly facingannular face, the said enlargement having bores extending through it andopening through the said face; the hub having portions of its moldedmaterial firmly imbedded against the said forward face, the said annularface and a part of. the shank adjacent to the said annular face, andalso having portions of the molded material filling the said bores.

EDWARD S. PRESTCN.

